Beneath the surface of Alaska’s partially frozen landscape, permafrost is being replaced by what might be considered its opposite: soil that stays unfrozen, even in winter.
Taliks are sections of year-round thawed soil that are wedged in areas with permafrost, generally between the lower layers that remain in freeze and the active surface layers that freeze and thaw with the seasons.
Now talik formation is speeding up, thanks to warmer winters, increased snowfall and the combination of those factors, according to research by permafrost experts at the University of Alaska Fairbanks.
The findings are detailed in a study published this week in the journal Nature Geoscience.
The study uses the temperature readings from long-established permafrost monitoring sites that have been sending data nearly continuously since as early as 1999. The 54 sites chosen for the investigation into talik formation ranged from the Canadian border area in the east to the Seward Peninsula in the west. The sites were both below and above the Arctic Circle and are places where permafrost is classified as discontinuous and where the state of freeze might be considered marginal. None of the sites had any unusual surface disturbance, such as wildfire scarring, that might have hastened thaw.
The state of thaw took a big jump in the winter of 2017-18, when new taliks were found at 24 of the sites, the study found. That coincided with exceptionally snowy and warm conditions that winter.
Warmer winter air temperatures are tied to talik formation, as is thick snow cover, which insulates the ground from the winter cold, said lead author Louise Farquharson, a research assistant professor at UAF’s Geophysical Institute.
The talik expansion is ominous, Farquharson said.
Since the presence of talik enables further thaw, talik expansion has implications for release into the air of carbon long sequestered in permafrost, she said. “This is going to really accelerate the amount of carbon mobilization that happens,” she said.
More talik also likely means more problems for structures and facilities on the ground surface, where thaw is already creating numerous maintenance and repair challenges in Alaska, Farquharson said. And there are yet-to-be determined effects on the flow of water over the landscape, including the possible new movement of contaminants and mercury through groundwater, she said.
Farquharson and her colleague calculated that a decade from now, if carbon emissions and warming continue at present rates, talik formation will be happening in up to 70% of the zone considered to be discontinuous permafrost — and by 2090, talik layers in some parts of the black spruce forest and other ecosystems will be nearly 40 feet thick.
Unlike the abrupt permafrost collapses found at eroding coastal bluffs, at areas of intense wildfire or at sinkholes in ice-rich areas of tundra landscapes, talik development is not obvious to the casual observer.
But it affects a lot more territory, Farquharson said.
“If we look at talik development, it’s a slower process but it’s much more widespread,” she said. “The taliks are going to form across the whole landscape.”
In time, that will include higher-latitude areas where the permafrost layers are, for now, unbroken. “This is going to expand northward into continuous permafrost,” she said.
Taliks can sometimes refreeze, if air temperatures are cold enough and snow is sparse enough. Farquharson and her colleagues actually found two examples of refreeze in their study, at Healy near Denali National Park and near Tanacross in the eastern part of Interior Alaska.
But do not expect any such refreezing after about 2030, according to the study. By then, if warming trends continue as expected, conditions will no longer allow refreezing, no matter how little snow falls.
“We’re kind of in a flickering-light phase right now,” Farquharson said.
The pattern of snow-linked talik formation persisted last winter, which featured record or near-record early winter snowfall in Interior Alaska. In Fairbanks, winter rain that created a durable coating of ice was followed by heavy snow, all creating havoc for drivers and for utilities. At Denali National Park, it was the snowiest December on record, according to the National Weather Service. Heavy snow collapsed the roof of the only grocery store in Delta Junction, about 90 miles southeast of Fairbanks.
Soil temperatures over the past winter were “significantly warmer” than the previous winter, Farquharson said. “That snowfall wasn’t good for permafrost,” she said.
For Fairbanks and the area around it, patterns of snow and winter precipitation have changed in the past decades, but in somewhat complicated ways, said Rick Thoman, a scientist with the Alaska Center for Climate Assessment and Policy at UAF.
Total winter snowfall in the region hasn’t increased or decreased, but the snow season has become compressed, Thoman said. “We’re getting more snow in a shorter period of time,” he said. Meanwhile, winter rain events, such as the one that drenched Fairbanks last winter, have become more frequent, he said.
There is a climate-change link to that precipitation pattern. The Bering Sea has become, over time, less icy, allowing more evaporation from open water later in the year, he said. “In Interior Alaska, that’s the primary source of moisture in the wintertime,” he said.